A wide variety of types of hybrid architectures of a drivetrain of a motor vehicle are basically known which combine an internal combustion engine and an electric machine in order to enable the motor vehicle to be driven efficiently. In general, a distinction is made between three different stages of hybridization, which differ in particular with regard to the contribution made by the electric machine to the drive torque.
In the case of so-called micro-hybrid vehicles, it is generally the case that an electric machine is provided for an automatic start-stop facility and for brake energy recovery for the purpose of charging a relatively small starter battery. In this case, the electric machine is normally not used for driving the vehicle.
By contrast, in the case of so-called mild hybrids, the electric machine provides assistance to the internal combustion engine in order to realize increased performance. Furthermore, the energy that arises during a braking process can, with suitable configuration of the drivetrain, be at least partially recovered in a generator mode of the electric machine.
By contrast to the hybridization variants described above, full hybrid vehicles can be driven entirely by the electric machine over relatively long periods of time. In the case of such vehicles, it may for example be provided that the internal combustion engine merely drives an electrical generator, the electrical generator supplying electrical energy to the electric machine in order to generate a drive torque and/or charging a battery. It is therefore possible for use to be made of an internal combustion engine of smaller dimensions than in motor vehicles with similar performance characteristics. Moreover, the internal combustion engine can be operated in an efficient power range, because power peaks can generally be covered by extracting energy from the battery.
Full hybrid architectures are also known in which the drive torque is provided either by the electric machine or by the internal combustion engine depending on demand. The electric machine and the internal combustion engine are in this case selectively coupled to or separated from the drivetrain by means of suitable clutches.